Acoustic diaphragm



Oct. 27, 1931. v, HOUGHTON I 1,829,355

ACOUSTIC DIAPHRAGM Filed July 29, 1930 5 Sheets-Sheet l f INVENTOR Oct. 27, 1931. k v HQUGHTON 1,829,355

ACOUSTIC DIAPHRAGM Fil ed July 29, 1930 s Sheets-Sheet 2 Oct. 27, 1931. v. T. HOUGHTON 1,329,355

'ACOUSTIC DIAPHRAGM Filed July 29, 1930 3 Sheets-Sheet 5 /3 I5 77 )mvw @WWIKN Patented Oct. 27, 1931 UNITED STATES PATENT OFFICE VERNON T. HOUGHTON, OF BRONXVILLE, NEW YORK, ASSIGNOR TO LEKTOPHONE COR- PORATION, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE ACOUSTIC DIAPHRAGM Application filed July 29,

This invention relates to diaphragms for loudspeakers.

The type of loudspeaker diaphragm now most extensively used, comprises a cone, a

rigid frame, and a substantially flat annular rim portion interposed between the edge of the cone and the frame and serving as a flexible connection between the cone and the frame to permit axial movement of the cone. By flat is meant that the plane of the rim extends substantially at right angles to the aXis of the cone. It has been common practice to make the cone out of paper and the rim out of some other material, such as leather. In some cases the rim is also made out of paper but is formed separately from the cone, as by stamping it from a flat sheet of paper. In either case, the rim must be glued to the edge of the cone and this necessarily causes the diaphragms to differ as to their characteristics, and in any event constitutes a step which it is desirable to eliminate to cheapen the cost of manufacture. Attempts have been made to produce a diaphragm in which the cone and the flat rim portion are integral and made-of the same material in order to eliminate the expense incident to gluing on the rim, and to eliminate the necessity of using material like leather for the rim, which is quite expensive. For instance, it has been proposed to mold or press diaphragms from fabric, such as buckram, in which the cone and rim are in one piece, but as the fabric suitable for making such diaphragms is quite expensive, the cost of the diaphragms cannot be materially reduced in this way. An ideal way is to press or otherwise form a cone and an integral rim from paper, using as the'starting material a fiat sheet of inexpensive paper. It has been proposed to mold a diaphragm from paper pulp so that the cone and flat rim will be in one piece, but this requires the use of elaborate machinery and the diaphragms so made are not uniform as to their characteristics. So far as I am aware, no one has solved the problem of pressing or otherwise forming an inexpensive and satisfactory diaphragm of the cone and integral flat rim type from paper,

using as the starting material a flat sheet of 1930. Serial No. 471,455.

paper, and it is the principal object of the present invention to provide such a diaphragm.

Another object of the invention is to provide a diaphragm having a cone and a substantially flat rim portion in which the cone has great freedom of motion in an axial di- 'rection, but is firmly supported in a radial direction.

A further object of the invention is to provide an improved method of making diaphragms having the foregoing characteristics.

Other objects of the invention will hereinafter appear.

The invention is illustrated in the accompanying drawings, in which- Figure 1 is a perspective view of one type of diaphragm constructed in accordance with the invention.

Figure 2 is a side view of the diaphragm shown in Figure 1.

Figure 3 is a transverse section taken on the line 33 of Figure 4.

Figure 4c is an enlarged plan view of a small section of the diaphragm showing one set of corrugations that are formed in the edge of the cone and the adjoining portion of the rim.

Figures 5 and 6 are plan views of the paper blank showing the manner in which it is creased to provide for the subsequent bending of the paper or formation of the corrugations.

Figures 6 and 6 are fragmentary views of opposite sides of the paper blank, showing in full lines the creases that are placed on one side of the blank and in dotted lines the creases that are placed on the opposite side.

Figure 7 is a perspective view of a modified form of diaphragm constructed in accordance with the invention.

Figures 8 and 9 are plan views of the paper blank, showing the manner it; which the blank is creased on opposite sides to provide for the subsequent bending of the paper or formation of corrugations of the kind shown in Figure 7.

Figures 9 and 9 are fragmentary views of opposite sides of the blank, showing in full A simple paper cone can readily be formed from a flat circular sheet of paper by cutting a sector from it and cementing together the radial edges of the sector. My diaphragm may be considered as such a simple cone in which a certain amount of fullness is gathered in or taken up along a circumferential line corresponding with the line of juncture between the cone and the flexible rim in the finished diaphragm. The taking up of the fullness progressively increases from the outer edge of the diaphragm to said line of juncture, and progressively decreases from said line until it disappears a certain distance up the walls of the cone, in such a way that a marginal portion of the simple cone can assume a substantially flat condition because the inner circumference of such marginal portion can be contracted. This marginal portion ultimately constitutes the above mentioned flexible rim portion of the finished diaphragm. The movement of the marginal portion of the simple cone to this new flat position, with the attendant contraction of its inner circumference, necessitates also a contraction of the circumference of that portion of the cone which adjoins the rim in the finished diaphragm. The fullness is so taken up in the simple cone as to bring this about. This is preferably accomplished by a system of corrugations as hereinafter described, provision being made for permitting a hinge action along the line of juncture of the cone and rim portion in the finished diaphragm, and the corrugations being preferably so formed as to carry out one of my objects of permitting great freedom of movement of the cone by allowing the circumferential edge portion of the cone and the inner circumferential portion of the rim to expand and contract as the cone vibrates.

Referring first tothe diaphragm shown in Figures 1 to 4 inclusive, it comprises a cone 1 and an integralrim portion 2 which is substantially flat, i. e., it lies in a plane extending. substantially at right angles to the axis of the cone. The rim portion 2, although integral with the cone, assumes a flat condition, due to the provision of a series of radial corrugations 3 formed in the rim portion of the diaphragm. These corrugations are wider where the rim joins the cone and taper to a point and fade out toward the edge of the rim. Preferably they do not extend entakes place along the zigzag lines 9.

tirely to the outer edge of the rim as it is desirable to leave an uncorrugated outer edge portion on the rim which can be clamped in c amping rings or otherwise secured to a rigid support. The edge portion of the cone 1 is provided with similar corrugations 4. The corrugatlons 1n the cone are wider near the edge portion of the cone and preferably extend but a short distance up the walls of the cone where each one tapers to a point and fades out. The corrugations 3 and 4 are preferably con'cave when viewed from the outside of the diaphragm. Inasmuch as the rim 2 forms an angle with the walls of the cone, provision must be made for allowing each corrugation 3 to assume an angle with the corresponding corrugation 4 and provision must also be made for allowing a relative bending action or hinge action between the corrugations when the cone vibrates. This is accomplished in the diaphragm of Figures 1 to 4 by providing a corrugation 5 between each corrugation 3 in the rim and the corresponding corrugation 4 of the cone. The corrugations 5 are convex when viewed from the outer side of the diaphragm. The crest 6 of each corrugation 5 is in line wlth and forms a continuation ofthe bottom bend or anti-crest 7 of the corrugation 4 and the bottom or anti-crest 8 of the corrugation 3, but the crest 6 forms an angle with the anti-crests 7 and 8 of the corrugations 4 and 3 when viewed from the side, as best shown in Figure 3. The bends or anticrests 9 formed by the intersection of the faces of the corrugations 5 with the faces of the corrugations 3 and 4, form two circumferentially extending zigzag lines as best shown in Figure 1.

When the diaphragm is mounted in a frame (not shown), as by mounting the outer edge portion of the rim 2 in clamping rings, and when the cone is vibrated at its apex by any suitable motor (not shown), a hinge actiin s the cone vibrates, the corrugations 3 and 4 expand and contract. This action is freely permitted by the corrugations 5 which expand and contract with them and, therefore,

the cone has considerable freedom of move- 1' ment in an axial direction.

The diaphragm shown in Figures 1 to 4,

. may be made by forming a flat sheet of paper into 'a cone and then pressing the corrugations into the cone so that the diaphragm assumes the form shown in the drawings. Preferably, however, the paper blank is first creased as shown in Figures 5 and 6, by suitable creasing dies or rollers. When paper is creased with creasing dies of the proper shape, the paper has a tendency to bend either in one direction or the other. It will be assumed that the dies used for creasing the blank are such that a crease in the outer surface of the diaphragm, as for instance,

one of the creases 7 will cause the adjacent surfaces to have a tendency to form an angle that is concave when viewed from the outer surface of the diaphragm, or in other words, to make the crease 7 an anti-crest. One side of the blank should then be creased in the manner shown in Figure 5 to ultimately fo: m the anti-crests and bending lines 7 and 9. The opposite side of the blank should be creased as shown in Figure C. to ultimately form the crests or bending lines (3 and 10. Figures 6 and 6' show in full lines the creases on one side of the blank. and in dotted lines the creases on the opposite side.

When a blank so creased is folded into cone shape, and the portion which ultimately forms the rim is bent up. the surfaces adjacent the creases may be moved by hand to their new positions to form the corrugations because the creasing imparts to the faces of the corrugations a strong tendency to assume those new positions. However. if it is desired to do this on a machine, a creased blank may be placed in a die press or passed between die rollers having male and female forn'iing surfaces to move the faces of the corrugations to their final desired posit ons. In either case there is a moving of the surfaces adjacent the creases to their new positions to form the corrugations within the meaning of the language of the method claims regardless of whether this is brought about by hand or by the use of machinery. Even when the corrugations are formed in a die press or by die rollers, the preliminary creasing of the blank facilitates the formation of the corrugations. As the provision of the corrugations 4 in the edge portion of the cone have a tendency to alter the original angle formed between this portion of the cone and the cone axis, the blank is preferably provided with a circular crease 11 where the corrugations 4 terminate to permit the walls of the cone to bend slightly at this crease, as best shown in Figures 1, 2 and 3.

If the corrugations 3 do not extend entirely to the outer edge of the rim portion 2, it is preferable to provide the rim with a radial split 12 at the end of each corrugation 3, as.

this enables the rim its'fiat condition.

The modified form of diaphragm shown in Figures 7 to 11 inclusive, has corrugations 3 provided in the rim, and corrugations 4 in the edge portion of the cone, these corrugations being similar to the corrugations 3 and 4 in the diaphragmdescribed above. excent that they are convex when viewed from the outer side of the diaphragm. They have crests l3 and anti-crests 14 where. their surfaces intersect the uncorrugated surface of the cone and the uncorrugated surfaceof the rim. The manner in which the corrugations 8 are allowed to assume an angle with the corrugations 4', the manner in which the to more readily assume hinge action betweenthem is permitted, and the manner in which the corrugations 3 and 4 are permitted to expand andcontract when the cone vibrates, are taken care of in a different way from that shown in Figures 1 to 4. In this case the corrugation 15, corresponding with the corrugation 5 in Figures 1 to 4, is concave when viewed from the outer side of the diaphragm and has a bend or anti-crest 16 which extends circumferentially of the diaphragm. The corrugation 15 is bounded by bends or crests 17 in such a way that the circumferential width at the base of the corrugation 15 is less than the circumferential width at the base of the corrugations 3 and 4. Extending down each wall of each corrugation 3 and 4' there is a bend or anti-crest 18. each of which extends from a point 19 where the lines 17 intersect the crests 13 to a point 20 where the line 14 of. the corrugation 3 meets the corresponding line 14 of the corrugation 4. The surfaces at either side of each line 18 are con ave when viewed from the outer side of the diaphragm. The line 18, together with the adjacent line 17, constitute two arms of a triangle, the base of which is formed by a bend or crest. 21. The surfaces at either s de of the crest 21 are con vex when viewed from the outer side of the diaphragm. The crests 21 are in alignment with the anti-crests 16 of the corrugations 15. The lines that constitute crests are lines 13, 17 and 21. The lines that constitute anticrests are lines 14, 16 and 18. As the points 22 where the lines 17 intersect the line 16 are elevated above points 20, the corrugations 3 and 4 can expand and contract as the cone vibrates. During this expanding and contracting action, the points 20 approach and recede while the points 22 remain a fixed distance apart. This is accompanied by a slight bending or hinge lines 21 and the lines 18, in addition to the bending or hinge action that takes place along the crests 13 of the corrugations and along their anti-crests 14.

The diaphragm shown in Figures 7 to 11 inclusive, may be made in the same way as the diaphragm of Figures 1 to that the paper may first be shaped into a cone and the corrugations pressed in the walls of the cone by suitable dies so that the diaphragm will assume the form shown in Figure 7, and if desired. this may be preceded by the creasing of the blank in the manner shown in Figures 8, 9, 9 and 9 The procedure of creasing the blank shown in these figures is the same as that described above in connection with Figures 6. (3 and 6. the only difference being that the creases are so arranged as to produce the different type of corrugations. As the propercreasing of the blanks produces a tendency for the surfaces of the corrugations to assume their final desired positions. and as the surfaces adjacent the creases may action along the lines 17, the

armature is capable of a large amplitude of movement, as in an electrodynamic motor. hen such a motor is employed, the rim of the diaphragm should have great flexibility and the cone should be capable of a large amplitude of movement. The advantage of allowing the edge portion of the cone and the inner edge portion of the rim to expand and contract asthe cone vibrates, will be more fully recognized when it is understood that a paper cone with a substantially flat paper rim is not capable of a large amplitude of movement, because every point on the inner circumference of the rim tends to swing in an arch of a circle which is convex with respect to the axis of the cone. This tends to expand and contract the base of the cone and the inner edge portion of the rim, but as paper does not readily expand and' contract, the movement of the cone is necessarily limited. If the rim portion of diaphragms now inuse is made sufficiently flexible to permit a large amplitude of movement of the cone, then the cone is not properly supported in a radial direction, and this is particularly serious in the case of an electrodynamic speaker, because any sagging of the cone tends to make the electrodynamic coil of the motor contact with the walls of the annular air gap.

In my diaphragm, the cone is always firmly supported in a radial direction in spite of the freedom with which the cone can move in an axial direction. In order to give an idea of how much movement the cone of my diaphragm is capable of, it might be stated that in a diaphragm having a cone whose basal diameter is about ten inches and a rim about an inch and a quarter wide, the cone may be moved about three-quarters of an inch but, of course, in operation it would never be required to move that distance. Throughout the movement of the cone the elastic restoring force of the rim remains nearly constant, this being a factor which aids in reducing distortion in the reproduction of sounds.

Good results have been obtained with diaphragms in which the corrugations are about an inch wide and extend about an inch into the rim and an inch up the walls of the cone, these dimensions having been found suitable for a diaphragm whose cone is about ten inches in diameter and whose rim is about an inch and a quarter wide, but obviously these dimensions, as well as the particular configuration of the corrugations hereinbefore described, may be departed from.

While the invention seeks mainly to overcome the difficulties that have been encounteredwith diaphragms in which the cone is made of paper and in which the cone and also the rim are made of paper, and while the invention applies particularly to dia. phragms 'of that type, nevertheless the invention may be app-lied to diaphragms made of other materials where it is desired to give the diaphragms any advantage or characteristic which might be derived from the use of the invention herein disclosed.

It will now be seen that a diaphragm constructed in accordance with this invention maybe made throughout of inexpensive material and manufactured at a small cost. It

i is well adapted for quantity production as the process of making it is simple and enables a large number of them to be manufactured in a short interval of time. Moreover, they are all substantially uniform as to their characteristics, which is not the case with diaphragms as now constructed.

I claim 1. An acoustic diaphragm comprising a conical portion made of paper, and a rim portion extending in a plane substantially at right angles to the axis of the conical portion, and means which renders the circumference of the base of the conical portion expansible and contractible.

2. In an acoustic diaphragm in accordance with claim 1, means which renders the inner circumference of the rim portion expansible and contractible.

3. An acoustic diaphragm comprising a conical portion and an integral rim portion both made of paper, means which renders the circumference of the base of the conical portion expansible and contractible, and means which renders the inner circumference of the rim portionlexpansihle and contractible.

4:. An acoustic diaphragm comprising a conical portion and a supporting portion at the edge of the conical portion. the conical portion being provided with radial corrugations permitting the cirgumference of the base of the conical portion to expand and contract, and means associated with said supporting portion to permit such expansion and contraction;

5. An acoustic diaphragm comprising a conical portion and a rim portion extending in a plane substantially at right angles to the axis of the conical portion, the conical portion having corrugations that are wider near the rim portion than towards the apex of the conical portion, and the rim portion having corrugations that are wider near the inner circumference of the rim portion than towards the outer circumference of the rim portion.

6. An acoustic diaphragm in accordance with claim 5, in which the corrugations in the conical portion and the rim portion are radial.

7. An acoustic diaphragm comprising a conical portion and a rim portion extending in a plane substantially at right angles to the axis of the conical portion, the conical portion having corrugations that are deeper near the rim portion than towards the apex of the conical portion, and .the rim portion having corrugations that are deeper near the inner circumference of the rim portion than towards the outer circumference of the rim portion.

8. An acoustic diaphragm comprising a conical portion and an integral rim portion extending in a plane substantially at right angles to the axis of the conical portion, each of said portions having tapering corrugations that are wider at the juncture between the conical and rim portions and fade out at points remote from said uncture.

9. An acoustic diaphragm comprising a conical portion and an integral rim portion extending in a plane substantially at right angles to the axis of the conical portion. the conical portion having corrugations extcnding towards its juncture with the rim portion, and the rim portion also having corrugations extending toward said juncture, each corrugation of the conical portion meeting a corrugation of the rim portion, there being an additional corrugation interposed between each corrugation of the each adjoinin corrugation of the rim portion to permit the rim to assume its angle with the walls of'the conical portion and to permit a hinge action between the conical portion and the rim portion.

10. An acoustic diaphragm in accordance with claim 9, in which all of said corrugations are expansible and contractible.

11. An acoustic diaphragm comprising a conical portion and a rim portion extending in a plane substantially at right angles to the axis of the conical portion, the conical portion "having corrugations extending towards its juncture with the rim portion, and the rim portion also having corrugations extending towards said juncture,'each corrugation of the conical portion meeting -'a""corrugation of the rim portion, means hereby the corrugations of each pair may assume an angle corresponding with the angle between the walls ot' the conical portion and the rim portion and said means permitting a hinge action between the corrugations of said pair. 12. An acoustic diaphragm comprising a conical portion and a rim portion extending in a plane substantially at right angles to the axis of the conical portion, the conical portion having corrugations extending towards its juncture with the rim portion, and the rim 5 portion also having corrugations extending conical portion andtowards said juncture, each corrugation of the conical portion meeting a corrugation of the rim portion, and means to permit expansion and contraction of the corrugations.

13. The method of making an acoustic diaphragm of the cone and flat rim type which comprises forming a flat sheet of material into a simple cone and then gathering in the fullness along a line that corresponds with the line of juncture of the conical and rim portions of the finished diaphragm so that the amount of fullness gathered in is greatest along said line and progressively decreases towards the apex of the conical portion and towards the edge of the diaphragm whereby a marginal portion of the diaphragm can assume a substantially flat position to constitute the rim portion of the finished diaphragmw 14. The method of making an acoustic diaphragm which comprises creasing a flat blank, forming the blank into a cone, and moving the surfaces adjacent said creases to new positions to form corrugations in thediaphragm whose bends correspond with the creases in the blank.

15. The method of making an acoustic diaphragm which comprises creasing a flat blank on one side with creases that tend to cause the adjacent surfaces to concave in one direction, creasing the opposite side of the blank with creases that tend to cause the adjacent surfaces to concave in the opposite direction, forming the blank into a cone and moving the surfaces adjacent said creases to the positions they tend to seek, to form corrugations whose bends correspond with the creases in the blank.

16. The. method of making a corrugated diaphragm which comprises creasing a fiat blank on. one side with creases that correspond with the crests of the corrugations,

and creasing the opposite side of the blank with creases that correspond with the anticrests of the corrugations, forming the blank into a cone and moving the surfaces adjacent the creases to new positions to form the corrugations.

17. An acoustic diaphragm comprising a cone, an annular rim, and means which renders the circumference of the base of the cone expansible and contractible.

18. An acoustic diaphragm comprising a cone, an annular rim, and means which renders the inner circumference of the rim expansible and contractible.

19. In the method of making an acoustic diaphragm of the cone and flat rim type the step which comprises gathering in the material of the diaphragm along a line that corresponds with the line of juncture of the conical and rim portions of the finished diaphragm so that thenmount of material gath ered in is greatest along said line and pro- 

